The invention, in some embodiments thereof, relates to polynucleotides and polypeptides involved in plant-fiber development and methods of using same.
Cotton and cotton by-products provide raw materials that are used to produce a wealth of consumer-based products in addition to textiles including cotton foodstuffs, livestock feed, fertilizer and paper. The production, marketing, consumption and trade of cotton-based products generate an excess of $100 billion annually in the U.S. alone, making cotton the number one value-added crop. In spite of the growth of synthetic fibers in the last 50 years, cotton still accounts for approximately 50% of the world's textile fiber. Even though 90% of cotton's value as a crop resides in the fiber (lint), yield and fiber quality has declined, especially over the last decade. This decline has been attributed to general erosion in genetic diversity of cotton varieties, and an increased vulnerability of the crop to environmental conditions.
Cotton fibers can be obtained from many varieties of cotton with a range of characteristics for various applications. Cotton fibers may be characterized according to a variety of properties, some of which are considered highly desirable within the textile industry for the production of increasingly high quality products and optimal exploitation of modern spinning technologies. Commercially desirable properties include length, length uniformity, fineness, maturity ratio, decreased fuzz fiber production, micronaire, bundle strength, and single fiber strength. Much effort has been put into the improvement of the characteristics of cotton fibers mainly focusing on fiber length and fiber fineness. In particular, there is a great demand for cotton fibers of specific lengths.
Several approaches can be used to improve the characteristics or yield of cotton fibers. Variety improvement of cultivated cotton plants has been performed by cross breeding. However, breeding is relatively slow and inefficient, and the degree of variability which can be achieved is limited to the existing genetic diversity. In addition, plants can be treated with hormones such as auxin, gibberellin, cytokinin, ethylene or brassinolide [see e.g. U.S. Pat. No. 5,880,110]. However, no measurable effect of the hormones has been documented, making practical use of these hormones on a large scale highly unlikely. Alternatively, variety improvement can be achieved by genetic engineering. In recent years, a remarkable progress has been made in plant genetic engineering with the successful variety improvement of commercially important crop plants such as cotton, soybean, corn, and canola. The broad acceptance of genetically engineered cotton in the leading producing countries make it an attractive candidate for genetic engineering for improvement of fiber yield and/or quality. For example, introducing a gene coding for an insecticidal protein toxin produced Bacillus thuringiensis (BT) into a cotton plant has improved insect resistance. In addition, cotton plants with improved herbicide (Glyphosate) resistance have been genetically engineered by the introduction of a gene coding for 5-enol-pyruvil-shikimic acid 3-phosphate synthetase.
A cotton fiber is composed of a single cell that has differentiated from an epidermal cell of the seed coat, developing through four chronological stages, i.e., initiation, elongation, secondary cell wall thickening and maturation stages. The elongation of a cotton fiber commences in the epidermal cell of the ovule immediately following flowering, after which the cotton fiber rapidly elongates for approximately 21 days. Fiber elongation is then terminated, and a secondary cell wall is formed and grows through maturation to become a mature cotton fiber.
Little is known about the genetic control of cotton fiber initiation and elongation. Since both cotton fibers and Arabidopsis trichomes are developed from single epidermal cells it was suggested that they both share similar genetic regulation (Reviewed at Wagner G. J. et. al. 2004). In Arabidopsis, a large number of studies have revealed extensive information on the genetic mechanisms regulating trichome initiation and elongation. Several studies demonstrated the similarities between trichome and fiber by showing that cotton fiber specific promoters confer trichome specific expression in arabidopsis and tobacco plants (Kim and Triplett, 2001; Hsu et. al. 1999; Liu et. al. 2000, Wang et al. 2004). Most of the research that studies fiber development uses arabidopsis trichome as a model system to identify cotton genes in a small scale manner (Kim and Triplett, 2001; Wang et al. 2004).
Several candidate genes associated with the elongation and formation of cotton fibers have been identified. For example, five genes from cotton plants which are specifically expressed at the cotton fiber elongation stage were identified by differential screening and display methods [U.S. Pat. No. 5,880,100 and U.S. Pat. Nos. 5,932,713, 6,225,536 and 6,166,294].
WO0245485 describes methods and means to modulate fiber quality in fiber-producing plants, such as cotton, by modulating sucrose synthase (a sugar important for cell wall synthesis) activity and/or expression in such plants.
U.S. Pat. No. 6,472,588 and WO0117333 provide methods of increasing the quality of cotton fiber (e.g., strength, length, fiber maturity ratio, immature fiber content, fiber uniformity or micronaire) by transforming a cotton plant with a DNA encoding sucrose phosphate synthase.
WO9508914 discloses a fiber producing plant comprising in its genome a heterologous genetic construct which includes a fiber-specific promoter and a coding sequence encoding a plant peroxidase, such as a cotton peroxidase.
WO9626639 provides a method utilizing an ovary specific promoter sequence to express plant growth modifying hormones in cotton ovule tissue. The method permits the modification of the characteristics of boll set in cotton plants and provides a mechanism for altering fiber quality characteristics such as fiber dimension and strength.
U.S. Pat. No. 5,981,834, U.S. Pat. No. 5,597,718, U.S. Pat. No. 5,620,882, U.S. Pat. No. 5,521,708 and U.S. Pat. No. 5,495,070 disclose a method of genetically engineering a fiber-producing plant and the identification of cDNA clones useful for identifying fiber genes in cotton.
U.S. patent applications 2002049999 and 2003074697 disclose cotton plants of the genus Gossypium expressing endoxyloglucan transferase, catalase or peroxidase with improved cotton fiber characteristics.
WO 01/40250 provides a method of improving cotton fiber quality by modulating transcription factor gene expression.
WO 96/40924 provides novel DNA constructs which may be used as molecular probes or alternatively inserted into a plant host to modify transcription of a DNA sequence-of-interest during various stages of cotton fiber development.
EP0834566 discloses a gene which controls the fiber formation mechanism in a cotton plant.
Validation of genes which improve cotton fiber yield and quality in vivo requires a reliable model system for cotton fiber development. Models in other plant platforms, such as trichome cells and root hairs, are widely accepted for cotton fiber development. However measuring changes in growth rate, cell length and thickness is not easy because of the small size, difficult access to and lack of uniformity in sizes. The present inventors have analyzed tomato seed hairs for their possible use as a model tissue for cotton fiber development (WO2005/121364 which is incorporated herein by reference) and demonstrated a high correlation between tomato seed hair and cotton fiber.
The generation of stably transformed transgenic plants to assess gene function is a lengthy manipulative process. As an alternative, foreign gene expression in plants is often performed using transient transformation of cells or tissues. Agrobacterium mediated transient gene expression (agroinfiltration) in plant leaves has become the favorite choice in many gene functional analyses (Kapila et al., 1997; Yang et al., 2000; Goodin et al., 2002). There are existing protocols for transient gene expression in tissue-culture grown cotton fibers [such as Kim H J, et al., 2001]. Orzaez D., et al. 2006, developed an agroinfiltration-based system (agroinjection), which allows transient expression of foreign genes directly in tomato fruit tissues.